Interactive Tool
💰

Hidden 401(k) Boost

Most paychecks have headroom hiding in plain sight. Tell us where you stand, then slide. We'll show you exactly what each dollar you contribute really costs your take-home — and how much that builds into by retirement.

🛠️ Interactive Tool ✅ 100% Free 🔒 Save your plan

Your situation

All inputs stay in your browser. Numbers are rounded to whole dollars.
Default 67 (full SS retirement age)
For Child Tax Credit ($2,000 each)
Average effective state income tax rate
Before any deductions
Max % of pay employer matches dollar-for-dollar
The "sweet spot" trick: redirect overwithholding into your 401(k)
What's already in the account today (compounds at 7%)

Your 401(k) contribution

Slide to see what each contribution level really costs your paycheck — after the tax break.
0% 100% 10%
Slider = percent of the IRS 401(k) limit you contribute (currently $23,500/yr; +$7,500 catch-up at 50+).
Your contribution / paycheck
$0
Net paycheck drops by
$0
True cost per $1 saved
$0.00
Projected balance at retirement age
$0
at age 67 if you contribute through then
Based on 7% average annual growth.
Stop after 20 years
Balance at age 55
$0
Starting balance$0
You contributed$0
Match captured$0
Growth$0
Stop after 20 yrs, let it ride
Untouched until age 67
$0
Starting balance$0
You contributed$0
Match captured$0
Growth$0
Contribute through retirement
Balance at age 67
$0
Starting balance$0
You contributed$0
Match captured$0
Growth$0
See the tax math behind the numbers
Estimates only — not tax advice. Federal brackets use the 2025 IRS schedule and may not reflect the current year's published numbers. FICA is Social Security (6.2% up to $176,100 wage base) plus Medicare (1.45%, plus 0.9% additional Medicare over $200K single / $250K MFJ). State is a single approximate effective rate per state — Pennsylvania, New Jersey, and a handful of others tax 401(k) contributions at the state level; this model simplifies that. The "Saver's Credit," IRA contributions, Roth, HSA, ACA premium subsidies, and other phaseouts are NOT modeled. Standard deduction and Child Tax Credit are applied based on filing status only — itemized deductions are ignored. Your actual federal tax, state tax, FICA, and net paycheck will differ. Consult a qualified CPA or tax professional before changing your contribution or W-4 withholding.